Adjustable slit mechanism



P 1958 J. H. PAYNE, JR 2,852,684

ADJUSTABLE sun: MECHANISM Filed Dec. 22, 1955 lnvenror:

John H. Payne, Jr.,

;by. Walad c:

His Arrorney United States Patent ADJUSTABLE SLIT MECHANISM' John H. Payne, Jr., Ballston Spa,- N.' Y., assignor to General- Electric (Iompany, a corporation of New York Application December 22, 1955, Serial No. 554,723-

8 Claims. (Cl. 250-413) This" invention relates to mass spectrometry and more particularly to an improved adjustable slit mechanism for a mass spectrometer or the like.

In mass spectrometry, it is well known to provide a resolving slit through which an ion beam is to travel. In the past, it has been the practice to vary the resolving slit dimension and hence its resolving power by mechanical movement performed manually. Since the resolving slit is within the mass spectrometer tube where a high vacuum condition exists, it was a requirement in order to make the resolving slit adjustment that the mass spectrometer be shut down and the vacuum destroyed. This practice of course caused considerable'delay and expense in operation.

It'is therefore an object of this invention to provide an adjustable slit mechanism for use within a mass spectrometer tube which is capable of having its slit dimensions modified from without the tube and especially while-the mass spectrometer is in operation.

In accordance with the above object, an adjustable slit mechanism is provided which comprises a supporting structure having an opening therethrough to permit passage of an ion beam and means movably mounted on the structure to form a slit. The slit forming means is preferably a pair of L-shaped members having knife edges which are aligned substantially parallel when in mounted position on the supporting structure. The slit dimension is established in accordance with a plurality of biasing means arranged to act in opposing manner on the slit forming members to establish a net bias. A movement of the members will ensue in response to the net bias to establish a balance condition. An adjustment to establish a new slit dimension is obtained by modifying the bias of at least one biasing means to establish a net bias. In a preferred embodiment, the net bias on the slit forming means is obtained through opposing interaction of a resilient means, such as at least one coil spring and a conductor adapted to be in tensioned engagement with the slit forming means. Adjustment of the net bias is made by passing an electric current through the conductor to cause heating which will modify the degree of tension a controllable amount. Appropriate limits are established for the movement of the slit forming means by mechanical stops which are adjustably mounted on the supporting structure as part of the slit adjustment mechanism. Additionally, a shield is provided to limit the effect of emission from the conductor.

Thus, it can be appreciated that the mechanism of this invention having been provided with a means for adjusting the slit dimension which is electrically conditionable, a mass spectrometer using the mechanism can be operated during the times when the slit will have its resolving power modified since electrical conditioning can be performed from outside the spectrometer tube wherein it would be positioned.

The features of this invention which are believed to be novel are set forth with particularity in the appended Figure 3 is a plan of one of the L-shaped slit forming members.

Figure 4 is an end elevation from the left of structure of Figure 1 with the shield removed to disclose more clearly the details of the electrical conductor bias means.

Figure 5 is a perspective in partial section showing elements of the wire support of Figure 4.

Referring to Figures 1 and 2, there is shown an adjustable slit mechanism comprising a metallic supporting structure designated generally by numeral 10 having a cylindrical portion 11 with a centrally disposed square opening 12 therethrough and a pair of transversely extending portions 14' and 15 integral with the cylindrical portion and extending in spaced parallel separation on opposite sides of the opening to permit passage of an ion beam therebetween and therethrough in any well known manner.- Mounted in a parallel manner between the extending portions 14' andv 15 in spaced apart relation is a pair of L-shaped members 20 and 21 having mounting arms 22 and 23placed proximate and along the inner surfaces of the extending portions and through opening 12 and slit forming arms 24 and 25 extending in opposite directions transversely across theopening 12 so as to present oppositely facing knife edges 26 and- 27 in substantially parallel alignment to define a resolving-slit 28. Movement of-the knife edges to obtain variations in the width of slit 28 is obtained by hingedly connecting the mounting arms 22 and 23 near one end thereof through suitable hinging means such as balls which are pressed in any wellknown manner into suitable sockets 41in extending portions 14 and 15 and sockets 42 in members 20 and 21. Movement of the members 20 and 21 in a pivotal manner about the hinge connections is obtained through thebiasing action of a pair of coil springs 45 and 46 disposed between the members and coacting therewith to enlarge slit 28. As best seen in Figures 2 and 3, recesses 43 are provided in arm 22 to receive the ends of the coil springs. Like recesses 44 are provided in arm 23' to receive the opposite ends of the springs, the several recesses acting to fix the position of the spring and the point of the pivoting bias force. As best shown in Figure 4, biasing of the members in a direction to oppose the bias of the coil springs is a wire conductor 50 which is strung between blocks 51 and 53, which are .separat'edly and fixedly secured by screws 54 and 55 on the face 13 of cylindrical portion 11 proximate one end of slit 28 and block 52 which is also secured by screws 56 to the face of the cylindrical portion of supporting structure proximatelthe opposite end of the slit.

The wire 50 is to be of a type capable of being tensioned and having its tension characteristic modified by suitable electrical conditioning which causes the wire to increase its length to modify its bias on-the members 20 and 21, such as by passing an electric current therethrough to cause heating.

In stringing the wire 50 between the blocks as best seen in Figures 4 and 5, it is passed through opening 60in block 51, parallel openings; 61 and 62 in block- 52, and opening 63 in block 53. Wire 50- is also strung so as to pass on the outside of insulating spools 64 and 65 on Patented Sept. 16, 1958.

the slit forming arms 24 and 25. The spools which are fixedly secured to the slit forming arms 24 and 25 by pins 66 and 67 respectively or other suitable means may be provided with peripheral grooves into which the wire may seat to prevent slippage out of contact during operation of the device. Having threaded the wire through the openings in the blocks, a tension may be applied thereto in any well known manner which pulls upon the extending ends thereof. Set screws 57 and 58 are provided in the blocks 51 and 53 respectively to hold the wire firmly within the respective openings 60 and 63.

In accordance with a preferred practice, supporting structure and blocks 51, 52, and 53 are preferably metallic. In addition, wire conductor 50 is preferably uninsulated since it will conduct current to bring it to a heated condition to cause change in its length. In this case, blocks 51 and 53 are separated from each other to insulate the ends of wire 59 from each other and blocks 51, 52, and 53 are insulated from the supporting structure by suitable means such as a layer of mica strip 59 shown in Figure 5 to insulate wire conductor 59 from the supporting structure. Attaching screws 54, 55, and 56 are also insulated from the blocks or the supporting structure in any well known manner.

Limits to the range of pivotal movement are imposed upon the members and 21 by mechanical stops 70 and 71 extending from oppositely disposed radial openings 16 and 17 in cylindrical portion 11 of the supporting structure through keyhole slots 29 and in members 20 and 21 respectively and into opening 12. Threaded body portions 72 and 73 on the stops cooperate with threads in openings 16 and 17 to make the stops adjustable therewithin to regulate the magnitude of extension into the opening 12. Neck portions 74 and 75 extending from the body portions of stops through keyhole slots 29 and 30 connect with head portions 76 and 77 which act with the body portions to provide separated abutting surfaces to members 20 and 21 proximate the reduced ends of the keyhole slots. Assembly of the stops through the members is made during assembly of the members on the supporting structure by passing the head portions through the enlarged ends of the keyhole slots and then moving the members laterally until the neck portions are within the reduced ends of the slot. After hinging takes place, the hinge means and stops cooperate to prevent further lateral displacement.

Upon assembly of the parts, adjustment of the stops to establish the range of slit change, and the tensioning of the wire conductor, a cylindrical cuplike shield 31, shown in Figure l, is placed over the end so as to extend along the sides of cylindrical portion 11 of the supporting structure. This shield serves to limit the efiect of emission from wire conductor 50. In addition, the shield is provided with a slot 32 which is aligned during assembly in registry with slit 28 to permit the passage of an ion beam from within the adjustable slit mechanism to its target. Shield 31 may further be provided with openings 33 in the periphery thereof to align with openings 16 and 17 in the cylindrical portion to allow access with anappropriate tool for adjusting the stops, and other suitable apertures not shown through which the ends of wire conductor 50 may pass for external connections. The entire assembly may then be placed within a mass spectrometer tube of any well known type, not shown, in a manner to allow passage of the ends of wire conductor 5% to the outside for external connection. The mass spectrometer tube ultimately is evac dated, and variation of the slit 28 is etfectuated through wire element only. Thus, an electric current may be passed through wire conductor 50, the resulting heat causing it to expand so as to reduce the tension therein and its bias on spools 64 and 65 thus establishing a net bias on the members 20 and 21. The springs 45 and 46 are then allowed to expand in accordance with their bias to move the members to a new balance position so as to separate the knife edges 26 and 27 to enlarge the slit 28. Suitable means may be used with the adjustable slit mechanism to supply various amounts of current to provide various slit adjustments. The means may be part of a potentiometer or other suitable electrical regu lator, not shown, to control the mechanism while the instrument is in operation thus obviating the need for shutting down the mass spectrometer to modify the slit 28.

While in the embodiment of this invention as described above, both members 20 and 21 are mounted and formed to be movable toward and away from each other to vary the size of slit 28, it will be apparent that this invention could equally well be carried out by having one of the members stationary and providing only one movable member to cooperate therewith. Also, while the members are shown as pivoted, it would be possible for one or both of them to slide in grooves on the face of the cylindrical portion 11 of supporting structure 10. Further, although one of the biasing means is specifically shown to be a wire conductor, it will be apparent that this element may be an electrically conditionable biasing means in a difierent form and may be any conducting element whose application in the adjustable slit mechanism is such as to adapt it to engage one or both of the spools 64 and 65 for moving at least one of the members against the spring bias to vary the width of slit 28. Still further, while the wire 50 is shown as biasing the members toward one another and the springs 45 and 46 are arranged to bias the members apart, these functions could be reversed.

Therefore, while a particular embodiment of the subject invention has been shown and described herein, it is in the nature of description rather than limitation, and it will occur to those skilled in the art that various changes, modifications, and combinations may be made within the province of the appended claims, and without departing either in spirit or scope from this invention in its broader aspects.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an adjustable slit mechanism for a mass spectrometer or the like, the combination comprising a supporting structure, a pair of slit forming members movably mounted on said structure, said slit forming members having knife edges disposed substantially parallel to define a slit, resilient means imposing a bias in a first sense on said members for relative movement therebetween, and an electric conductor tensioned to bias said members in a sense opposing the bias of said resilient means, said conductor means being electrically conditionable to have its length modified to vary said slit.

2. In an adjustable slit mechanism for a mass spectrometer or the like, the combination comprising a supporting structure, a pair of members movably mounted.

on said supporting structure, said members having knife edges disposed substantially parallel to define a slit, resilient means biasing said members to enlarge said slit, and an electric conductor means tensioned to bias said members to reduce said slit, said conductor means being electrically conditionable to have its bias modified to vary the slit.

3. The adjustable slit mechanism of claim 2 in which said members comprise L-shaped members having a knife edge on the extremity of one arm of said L and hinge means for pivotally mounting said members on said supporting structure.

4. The adjustable slit mechanism of claim 2 in which said members comprise L-shaped members having a knife edge on the extremity of a short arm of said L and ball and socket hinges near the outer extremity of the long arm of said L pivotally mounting said members on said supporting structure.

5. The adjustable slit mechanism of claim 4 in which said L-shaped members are biased apart by coil springs coacting against said hinged long arms.

6. The adjustable slit mechanism of claim 2 in which only one of said members is movable.

7. The adjustable slit mechanism of claim 2 in which the relative movement of said members is restricted over a predetermined range by limit stop means adjustably mounted on said supporting structure.

8. The adjustable slit mechanism of claim 2 in which a shield is placed over said conductor means having the slit in registry with the slit formed by said knife edges References Cited in the file of this patent whereby said shield minimizes the effects of emission 10 2,492,993

from said conductor means.

UNITED STATES PATENTS Ulrey Mar. 9, 1937 Bleakney Nov. 12, 1940 Varian et al. Jan. 21, 1947 Norton Oct. 19, 1948 Harrison Jan. 3, 1950 

